// Copyright (c) 2021, gottingen group.
// All rights reserved.
// Created by liyinbin lijippy@163.com

#ifndef ABEL_CONTAINER_BTREE_TEST_H_
#define ABEL_CONTAINER_BTREE_TEST_H_

#include <algorithm>
#include <cassert>
#include <random>
#include <string>
#include <utility>
#include <vector>

#include "abel/container/btree_map.h"
#include "abel/container/btree_set.h"
#include "abel/container/flat_hash_set.h"
#include "abel/chrono/time.h"

namespace abel {

    namespace container_internal {

// Like remove_const but propagates the removal through std::pair.
        template<typename T>
        struct remove_pair_const {
            using type = typename std::remove_const<T>::type;
        };
        template<typename T, typename U>
        struct remove_pair_const<std::pair<T, U> > {
            using type = std::pair<typename remove_pair_const<T>::type,
                    typename remove_pair_const<U>::type>;
        };

// Utility class to provide an accessor for a key given a value. The default
// behavior is to treat the value as a pair and return the first element.
        template<typename K, typename V>
        struct KeyOfValue {
            struct type {
                const K &operator()(const V &p) const { return p.first; }
            };
        };

// Partial specialization of KeyOfValue class for when the key and value are
// the same type such as in set<> and btree_set<>.
        template<typename K>
        struct KeyOfValue<K, K> {
            struct type {
                const K &operator()(const K &k) const { return k; }
            };
        };

        inline char *GenerateDigits(char buf[16], unsigned val, unsigned maxval) {
            assert(val <= maxval);
            constexpr unsigned kBase = 64;  // avoid integer division.
            unsigned p = 15;
            buf[p--] = 0;
            while (maxval > 0) {
                buf[p--] = ' ' + (val % kBase);
                val /= kBase;
                maxval /= kBase;
            }
            return buf + p + 1;
        }

        template<typename K>
        struct Generator {
            int maxval;

            explicit Generator(int m) : maxval(m) {}

            K operator()(int i) const {
                assert(i <= maxval);
                return K(i);
            }
        };

        template<>
        struct Generator<abel::time_point> {
            int maxval;

            explicit Generator(int m) : maxval(m) {}

            abel::time_point operator()(int i) const { return abel::time_point::from_unix_millis(i); }
        };

        template<>
        struct Generator<std::string> {
            int maxval;

            explicit Generator(int m) : maxval(m) {}

            std::string operator()(int i) const {
                char buf[16];
                return GenerateDigits(buf, i, maxval);
            }
        };

        template<typename T, typename U>
        struct Generator<std::pair<T, U> > {
            Generator<typename remove_pair_const<T>::type> tgen;
            Generator<typename remove_pair_const<U>::type> ugen;

            explicit Generator(int m) : tgen(m), ugen(m) {}

            std::pair<T, U> operator()(int i) const {
                return std::make_pair(tgen(i), ugen(i));
            }
        };

// Generate n values for our tests and benchmarks. Value range is [0, maxval].
        inline std::vector<int> GenerateNumbersWithSeed(int n, int maxval, int seed) {
            // NOTE: Some tests rely on generated numbers not changing between test runs.
            // We use std::minstd_rand0 because it is well-defined, but don't use
            // std::uniform_int_distribution because platforms use different algorithms.
            std::minstd_rand0 rng(seed);

            std::vector<int> values;
            abel::flat_hash_set<int> unique_values;
            if (values.size() < static_cast<size_t>(n)) {
                for (int i = values.size(); i < n; i++) {
                    int value;
                    do {
                        value = static_cast<int>(rng()) % (maxval + 1);
                    } while (!unique_values.insert(value).second);

                    values.push_back(value);
                }
            }
            return values;
        }

// Generates n values in the range [0, maxval].
        template<typename V>
        std::vector<V> GenerateValuesWithSeed(int n, int maxval, int seed) {
            const std::vector<int> nums = GenerateNumbersWithSeed(n, maxval, seed);
            Generator<V> gen(maxval);
            std::vector<V> vec;

            vec.reserve(n);
            for (int i = 0; i < n; i++) {
                vec.push_back(gen(nums[i]));
            }

            return vec;
        }

    }  // namespace container_internal

}  // namespace abel

#endif  // ABEL_CONTAINER_BTREE_TEST_H_
